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Cellular mobile communication is the important thesis in the present scenario. It provides an economic growth in all countries. Mobiles phones are invented on the basis of radio communication. The first mobile phone was invented in 1973.Later it came to evolution as first generation (1G), second generation(2G),third generation(3G) and upcoming fourth generation(4G).

First generation was introduced in 1970.First generation use a standard known as AMPS(advanced mobile phone system),Nordic mobile telephone(NMT),Total access communication system(TACS). Use of semiconductor technology and microprocessor made device smaller ,lighter.It use analog technology. It provide only voice service and the speed is also slow due to analog system.

Second generation was introduced in 1990.It is developed to increase the transmission quality ,coverage etc..Second generation use Global system for mobile communication(GSM),Digital advanced mobile phone(D-AMPS),Code division multiple access(CDMA),Personal digital communication. It provide data and voice services. It uses digital communication and the speed is better than first generation. Then 2.5 G with general packet radio service(GPRS). It uses Code division multiple access (CDMA) and Time division multiple access(TDMA)

2.5 G is different from 2 G and it uses packet switching GPRS (general packet radio service) . It has been upgraded from GSM , it transfer data at 50kbps. Enhanced data for global evolution (EDGE) is another upgrade of 2.5 G, it transfer data rate 3 times faster than GPRS. And another upgrade of 2.5 G is CDMAone(IS-95B),it transfer data at 115Kbps.

Fig 3.2.5 generation

Third generation (3G):

Third generation provides multimedia application, it provide video calls , high speed data rate. It has data transfer rate upto 384 Kbps. It provides a service known as Universal mobile telecommunication system(UMTS) or IMT-2000. 3G use a single standard network all over the world.

Present scenario:

The present scenario in mobile communication is that all over the world use 3G Generation. It provides high speed internet data rate , video conferencing, GPS service etc...The mobile phone that has high ââ‚¬"speed downlink packet access(HSDPA) and universal mobile telecommunications system(UMTS) supports 3 G services.

Need of migration:

The main need of migration is to reduce the cost and increase the number of subscribers . The 3G uses High speed packet access service(HSPA) service . With the evolution of LTE(long term evolution) and Evolved Packet System (EPS), it migrates to 4 G. The 4 G provide the data rate at 10 times higher than the speed offered by the 3 G network. The advantage of 4 G network are

GPRS and EDGE both are mostly referred as 2.5 G technology because it does not provide high megabit data transfer for multimedia communication .

The 3GPP2 is classified as follows

1.one ââ‚¬"radio transmission technology(1xRTT)

2.Evolution data optimised.

3. EV-DO revision A.

4.EV-DO revision B.

5. Ultra mobile broadband.

1xRTT is generally referred as 2.5 G and revision version of 1xRTT is 1xRTT revision A and 1xRTT revision B ,it downlink data at 4.9Mbps.

LTE and UMB are mostly considered as fourth generation ,it download data at higher data rate.

The five different standard are

1.CDMA2000

2. W-CDMA

3.TD-CDMA/TD-SCDMA

4.DECT

5.UWC-136

Fig 4. IMT five different standard

CDMA2000,W-CDMA,TD-CDMA/TD-SCDMA all these three standard are used in 3G for full coverage and other two standard are used for short distance .

W-CDMA:

W-CDMA is a main technology that was first implemented in third generation. It is a spread spectrum modulation technique that supports both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) , it transfers data 10 times higher than 2G and also it can simultaneously transfer more number of data. The modulation technique used in W-CDMA is balanced QPSK for downlink and Dual channel QPSK for uplink. Convolution and turbo codes are used for channel coding, it uses code division multiple access. The transmission and reception efficiency at mobile station is 55dB and base station is 80dB .

CDMA2000:

CDMA2000 is different from W-CDMA , it uses two separate frequency for data and voice services. There are many evolution of CDMA.

Fig 5.evolution of CDMA

CDMA 1X EV-DO is one of the evolution of CDMA2000, it carries only data at the rate of3.1Mbps in forward and 1.8Mbps in reverse direction. But in CDMA 1X EV-DV it carries both the data and voice service. Next the CDMA 1xRTT and CDMA 3XRTT. RTT(radio transmission technology ) .In the CDMA2000 1xEV-D0 and CDMA 1xEV-DV , both use a channel bandwidth of 1.25MHz and it is poor for higher data transmission . and in CDMA1xRTT ,CDMA 3XRTT the spreading rate in lesser than data rate so it doesnââ‚¬â„¢t work good for video download. It transfer data at 144Kbps to 2Mbps.

Fig 6. Third generation

TD-CDMA and TD-SCDMA:

TD-CDMA uses Time Division Duplex technology(TDD).TDD is good in internet data transmission. It uses a unpaired spectrum for both uplink and downlink. Later TD-SCDMA has been developed by China academy of telecommunications technology(CATT), it eliminates interference caused to other TDD by using synchronisation technique . It provide full network coverage over macro ,micro and Pico cells.

TD-SCDMA uses TDD technology , by using different time slot data can be sent without traffic and also uses unpaired spectrum. It uses both Time division multiple access(TDMA) and Code division multiple access(CDMA). By using synchronisation data can be sent at different time slots. It uses QPSK,16QAM,HSDPA/8PSK/64QAM

HSPA (High speed packet access):

High speed packet access is a 3.5 G.

It has two protocols

1. HSDPA(High speed downlink packet access)

2.HSUPA(High speed uplink packet access)[18].

HSDPA:

After 3 G ,In 3.5 G High speed downlink packet access protocol (HSDPA) is used for mobile data transmission . HSDPA is the improved version from W-CDMA , it increases data rate five times higher than WCDMA and can transmit data at 10 Mbps and with MIMO it can transmit upto 20 Mbps. It can be used only from base station to mobile and not from mobile to base station . It uses QPSK, 16QAM, 64QAM modulation .It uses Adaptive modulation and coding system .

HSUPA:

HSUPA is used for uplink , it can transmit data at 5.8 Mbps .It is also known as Enhanced uplink (EUL).It uses BPSK modulation , Hybrid Automatic repeat request and it does not used adaptive modulation [19].

HSPA+:

HSPA+ is the improved version of HSPA. Using continuous packet connectivity and MIMO (Multiple input and multiple output), it provides high performance to video ,VOIP and all multimedia services .It uses same carrier for data and voice transmission .It uses 64-QAM modulation and it can transmit upto 21 Mbps[20].

LTE(Long term evolution):

LTE is the developed to provide high performance than HSPA+. It uses Internet protocol to transmit voice in packets. It uses OFDM(Orthogonal frequency division multiplexing ) modulation. OFDM is used for downlink ,it provide data rate upto 326 Mbps and SC-FDMA is used for uplink , it provide data rate upto 86.4Mbps in 20MHz BW. Turbo codes are used for encoding and Forward error correction codes for decoding[21].

Advantages of 3G:

1.It provides higher bandwidth.

2.Increased security and reliability

3. It provides packet based IP network.

4.Multimedia service.

Limitations of 3G:

The cost of implementing 3 G is high.

Require more power.

Base station must be closer

Cost of spectrum is high.

Fig 7. Technology comparison

Fourth generation:

Fourth generation is extended from third generation. It offers more bandwidth and services to the user . it uses internet protocol to provide high speed video and audio streaming . 4 G consider UMTS, OFDM, MIMO, WiMAX, SDR, TD-SCDMA. 4G provides data rate at 100Mbps for mobile user and 1Gbps for fixed user. The main aim of 4G is used to provide higher data rate and to reduce the blips when the device moves to different network. It uses IP network address. Fourth generation concentrate on two systems WiMAX and LTE(long term evolution).

LTE provides more bandwidth, increase in mobility, latency reduction. 4G has been developing based on two techniques 3xRTT and WCDMA. The problems in these technique can resolved using software defined radio .The new access technology Large area synchronised code division multiple access(LAS-CDMA) will support all future techniques.

Quality of service:

It is used to measure signal quality and service. QOS in 4G are bandwidth allocation, handoff ,varying channel characteristics. The QOS in 4G is approximated to 99.999%

Fig 8.Growth of mobile technology

Technology used in 4G:

Fourth generation(4G )technology uses Multi carrier Code division multiple access (MC-CDMA) and Orthogonally frequency division multiplexing (OFDM) using time division multiple access .MC-CDMA uses QPSK( Quadrature phase shift keying ) and OFDM uses higher modulation scheme QAM( Quadrature amplitude modulation). It uses multi carrier modulation ,each sub carrier is orthogonal to each other and sent data in parallel bit streams.OFDM receives data and it transform into analog signal using IFFT and sent to the RF transceiver . It does not allow multipath fading and delays and it provide good communication link. It also uses MIMO, this antenna technology is used to reduce the error and increase data rate .

Difference between 3G and 4G:

In 3G networks CDMA modulation scheme is used and in 4G ,in LTE, SC-FDMA(Single carrier frequency division multiplexing) is used and in WiMAX it uses OFDMA modulation (Orthogonal Frequency division multiple Access)[22]

LTE-ADVANCED:

LTE advanced is used in 4 G. It is developed based on the requirement specified by IMT(International Mobile Telecommunications).It provides a downlink data rate upto 1Gbps in stationary and 100Mbps when travelling and uplink data rate upto 30Mbps .It is 40 times faster than 3 G. It uses OFDM (orthogonal frequency division multiplexing) and also MIMO(multiple input multiple output)[23].

Coding technique :

It uses turbo codes, forward error correction that add redundancy bit to the transmitted data and concatenated coding technique is used to provide quality of service . It sent more number block with less bit error rate.

Ultra wide band :

It uses RF spectrum , UWB is used to avoid interference caused by other equipments and it does not allow inter symbol interference . The transmitted delay signal cause interference and UWB eliminate the inter symbol interference by generating UWB pulse . It reduces bit error rate.

Smart antenna:

Smart antenna is also known as adaptive antenna technology or MIMO(Multiple inputs and Multiple outputs) .It provides good channel capacity , it reduces multipath fading. It has slow varying traffic pattern and also allow to form beam on a particular area and MIMO antenna is used in LTE and LTE-advanced. Smart antenna increases the quality of service, increase channel capacity and bandwidth. It is used in both transmitter and receiver side . It provides quality of service and spectral efficiency.

Advantages of smart antenna:

1.Increase bandwidth

2. Increase coverage area.

3.Spectrum reuse.

Software defined radio:

Software defined radio (SDR) is an open wireless architecture .To make the development easier SDR is introduced. It is a collection of hardware and software technologies and all of these are implemented using modifiable software such as FPGA (Field programmable gate array), programmable system on chip, Digital signal processor(DSP)

Adaptive modulation and coding :

Adaptive modulation is used to achieve higher data rate . Adaptive modulation multi carrier system can achieve larger throughput. It uses a small time frequency channel and made it as approximation for every time slot it represent separate channel and channel optimisation and throughput is achieved for those channels.

Conclusion:

In mobile technology 4 G offers a single standard all over the world. It offers low cost implementation and efficient data transmission .The main aim of fourth generation is to provide high data rate for multimedia video streaming , audio streaming etc... There are several issues in research and development for improving the 4G technology .

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